simplify inhibit_rule description (#1137)

Most of the Prometheus docs are excellent! However, I found the `inhibit_rule` description confusing. This is my attempt to simplify the language. 50% of this pull request is me verifying that I understand how the `inhibit_rule`s work.
Signed-off-by: Frederick <fmoor@users.noreply.github.com>

content/docs/alerting/configuration.md

@@ -191,9 +191,10 @@ route:
 
 ## `<inhibit_rule>`
 
-An inhibition rule is a rule that mutes an alert matching a set of matchers
-under the condition that an alert exists that matches another set of matchers.
-Both alerts must have a set of equal labels.
+An inhibition rule mutes an alert (target) matching a set of matchers
+when an alert (source) exists that matches another set of matchers.
+Both target and source alerts must have the same label values 
+for the label names in the `equal` list.
 
 __Alerts can inhibit themselves. Avoid writing inhibition rules where
 an alert matches both source and target.__